共享运算符导致Jest测试失败

Question

我有一个发出HTTP请求的Angular服务.该服务的主要工作是刷新访问令牌并在请求结果为401时重试请求.该服务还能够宽限期地处理多个并发请求:如果有3个请求导致401,则令牌将只刷新一次,所有3个请求将被重播.以下GIF总结了此行为:

我的问题是我似乎无法测试这种行为.最初,我的测试总是因超时而失败,因为我没有调用我的订阅或错误方法.添加fakeAsync之后我再也没有得到超时,但我的观察者仍然没有被调用.我还注意到,如果我从tokenObservable中删除共享运算符,则会调用我的测试中的订阅,但通过这样做,我将失去多播的好处.

这是不能正常工作的测试

it('refreshes token when getting a 401 but gives up after 3 tries', fakeAsync(() => {
const errorObs = new Observable(obs => {
  obs.error({ status: 401 });
}).pipe(
  tap(data => {
    console.log('token refreshed');
  })
);
const HttpClientMock = jest.fn<HttpClient>(() => ({
  post: jest.fn().mockImplementation(() => {
    return errorObs;
  })
}));
const httpClient = new HttpClientMock();

const tokenObs = new Observable(obs => {
  obs.next({ someProperty: 'someValue' });
  obs.complete();
});

const AuthenticationServiceMock = jest.fn<AuthenticationService>(() => ({
  refresh: jest.fn().mockImplementation(() => {
    return tokenObs;
  })
}));
const authenticationService = new AuthenticationServiceMock();

const service = createSut(authenticationService, httpClient);

service.post('controller', {}).subscribe(
  data => {
    expect(true).toBeFalsy();
  },
  (error: any) => {
    expect(error).toBe('random string that is expected to fail the test, but it does not');
    expect(authenticationService.refresh).toHaveBeenCalledTimes(3);
  }
);
}));

这就是我在SUT中注入模拟的方法:

  const createSut = (
    authenticationServiceMock: AuthenticationService,
    httpClientMock: HttpClient
  ): RefreshableHttpService => {
    const config = {
      endpoint: 'http://localhost:64104',
      login: 'token'
    };
    const authConfig = new AuthConfig();

    TestBed.configureTestingModule({
      providers: [
        {
          provide: HTTP_CONFIG,
          useValue: config
        },
        {
          provide: AUTH_CONFIG,
          useValue: authConfig
        },
        {
          provide: STATIC_HEADERS,
          useValue: new DefaultStaticHeaderService()
        },
        {
          provide: AuthenticationService,
          useValue: authenticationServiceMock
        },
        {
          provide: HttpClient,
          useValue: httpClientMock
        },
        RefreshableHttpService
      ]
    });

    try {
      const testbed = getTestBed();
      return testbed.get(RefreshableHttpService);
    } catch (e) {
      console.error(e);
    }
  };

以下是被测系统的相关代码:

    @Injectable()
export class RefreshableHttpService extends HttpService {
  private tokenObservable = defer(() => this.authenthicationService.refresh()).pipe(share());
  constructor(
    http: HttpClient,
    private authenthicationService: AuthenticationService,
    injector: Injector
  ) {
    super(http, injector);
  }
  public post<T extends Response | boolean | string | Array<T> | Object>(
    url: string,
    body: any,
    options?: {
      type?: { new (): Response };
      overrideEndpoint?: string;
      headers?: { [header: string]: string | string[] };
      params?: HttpParams | { [param: string]: string | string[] };
    }
  ): Observable<T> {
    return defer<T>(() => {
      return super.post<T>(url, body, options);
    }).pipe(
      retryWhen((error: Observable<any>) => {
        return this.refresh(error);
      })
    );
  }

  private refresh(obs: Observable<ErrorResponse>): Observable<any> {
    return obs.pipe(
      mergeMap((x: ErrorResponse) => {
        if (x.status === 401) {
          return of(x);
        }
        return throwError(x);
      }),
      mergeScan((acc, value) => {
        const cur = acc + 1;
        if (cur === 4) {
          return throwError(value);
        }
        return of(cur);
      }, 0),
      mergeMap(c => {
        if (c === 4) {
          return throwError('Retried too many times');
        }

        return this.tokenObservable;
      })
    );
  }
}

它继承的类:

 @Injectable()
export class HttpService {
  protected httpConfig: HttpConfig;
  private staticHeaderService: StaticHeaderService;
  constructor(protected http: HttpClient, private injector: Injector) {
    this.httpConfig = this.injector.get(HTTP_CONFIG);
    this.staticHeaderService = this.injector.get(STATIC_HEADERS);
  }

由于某些未知原因,它不会在第二次调用时解析refresh方法返回的observable.奇怪的是,如果从SUT中删除tokenObservable属性中的share运算符,它就可以工作.它可能需要做一些时间安排.与Jasmine不同,Jest并不会模仿RxJs使用的Date.now.一种可能的方法是尝试使用来自RxJs的VirtualTimeScheduler来模拟时间,尽管这就是fakeAsync应该做的事情.

依赖关系和版本:

1. Angular 6.1.0
2. Rxjs 6.3.3
3. 开玩笑23.6.0
4. 节点10.0.0
5. Npm 6.0.1

以下文章帮助我实现了功能: RxJS:了解发布和共享运算符

Answer 1

我已经研究过这个，似乎我有一些想法为什么它不适合你：

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1) Angular HttpClient 服务在异步代码中抛出错误，但您是同步执行的。结果它破坏了共享运算符。如果您可以调试，您可以通过查看来发现问题ConnectableObservable.ts

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在您的测试中，连接仍将保持打开状态，而 HttpClient 异步代码中的连接取消订阅并关闭，以便下次创建新连接。

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要修复它，您还可以在异步代码中触发 401 错误：

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const errorObs = new Observable(obs => {\n   setTimeout(() => {\n     obs.error({ status: 404 });\n   });\n...\n

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但你必须等待所有异步代码都已执行完毕tick：

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service.post(\'controller\', {}).subscribe(\n  data => {\n    expect(true).toBeFalsy();\n  },\n  (error: any) => {\n    expect(error).toBe(\'Retried too many times\');\n    expect(authenticationService.refresh).toHaveBeenCalledTimes(3);\n  }\n);\n\ntick(); // <=== add this\n

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2）你应该删除你的以下表达式RefreshableHttpService：

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mergeScan((acc, value) => {\n    const cur = acc + 1;\n    if (cur === 4) { <== this one\n      return throwError(value);\n    }\n

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因为我们不想抛出错误value上下文错误。

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之后您应该捕获所有刷新调用。

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我还创建了示例项目https://github.com/alexzuza/angular-cli-jest

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只要尝试npm i一下npm t。

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  Share operator causes Jest test to fail\n    \xe2\x88\x9a refreshes token when getting a 401 but gives up after 3 tries (41ms)\n\n  console.log src/app/sub/service.spec.ts:34\n    refreshing...\n\n  console.log src/app/sub/service.spec.ts:34\n    refreshing...\n\n  console.log src/app/sub/service.spec.ts:34\n    refreshing...\n\nTest Suites: 1 passed, 1 total\nTests:       1 passed, 1 total\nSnapshots:   0 total\nTime:        4.531s, estimated 5s\nRan all test suites.\n

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也可以通过调试npm run debug

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